Here's why:
* The Towering Structure: Both Mont Saint-Michel and Hogwarts are perched on rocky outcrops, with towering structures that seem to reach for the sky. The imposing silhouette of the abbey on Mont Saint-Michel strongly resembles the imposing image of Hogwarts castle in the books and films.
* Medieval Architecture: Both Mont Saint-Michel and Hogwarts feature a blend of architectural styles, incorporating elements of medieval architecture, with Gothic spires, turrets, and gargoyles. The use of stone and the overall design of the structures reflect a sense of age and grandeur.
* Isolation and Mystery: Both locations are somewhat isolated and evoke a sense of mystery and magic. Mont Saint-Michel sits on a small island, accessible only by a causeway, which adds to its mystique. Similarly, Hogwarts is depicted as a secluded castle, hidden from the Muggle world, creating a sense of wonder and intrigue.
While J.K. Rowling has not explicitly stated that Mont Saint-Michel was her inspiration, the similarities are striking, and it's safe to say that the real-life structure likely played a role in shaping her vision for Hogwarts.